Banquo
Banquo is one of Macbeth's henchmen. The other is Fleance.
History
The two of them have twice assisted Macbeth in his schemes, once by stealing the Scrolls of Merlin for him, the other time by helping him in his attempt to claim Excalibur ("A Lighthouse in the Sea of Time," "Pendragon"). They also attended his wedding to Dominique Destine in Paris ("Sanctuary").
At some later date, Banquo and Fleance left Macbeth's service and eventually came to work for Castaway (a somewhat ironic move in view of Castaway being descended from Macbeth's old enemies Duncan and Canmore). They helped him set up and train the ordinary citizens whom Castaway recruited for the Quarrymen, and fought against Goliath and Elisa alongside him ("Nightwatch", "The Journey").
Banquo and Fleance are both aware of Macbeth’s true identity as the historical Macbeth.
Real World History
Banquo is never actually named in the series, but only in the ending credits. His name, of course, is a reference to the Banquo of Shakespeare's Macbeth, a former friend of Macbeth's. Macbeth later comes to fear and distrust Banquo when the Weird Sisters prophesy that Banquo's descendants will rule Scotland. He finally murders Banquo, although his son Fleance escapes, to eventually become the ancestor of James I of England. (Banquo and Fleance were, in fact, completely fictional, invented by the Stuarts to provide themselves with a distinguished Scottish ancestry. James's belief that he was descended from them seems to have been one reason for Shakespeare's negative portrayal of Macbeth in his play.)
Production Background
Voice Actor: Frank Welker